1. Field of the Invention
Embodiments of the invention relate to an organic light emitting device and, more particularly, to a white organic light emitting device which secures high efficiency and low voltage by applying co-deposition of an inorganic substance to a charge generation layer provided between adjacent light emitting stacks.
2. Discussion of the Related Art
In recent years, the coming of the information age has brought about rapid development in displays which visually express electrical information signals. In response to this, a great deal of research has been conducted to impart superior properties such as slimness, light weight and low power consumption to a variety of flat display devices.
Specifically, representative examples of flat display devices include liquid crystal display (LCD) devices, plasma display panel (PDP) devices, electroluminescent display (ELD) devices, electrowetting display (EWD) devices, field emission display (FED) devices, organic light emitting diode (OLED) display devices and the like.
Of these, organic light emitting display devices are considered to be competitive in applications which require no additional light sources, implement compact of devices and clearly render color.
Formation of an organic light emitting layer is required for such an organic light emitting display device.
Organic light emitting display devices may exhibit white color by laminating a stack structure including different colors of organic light emitting layers, instead of patterning the organic light emitting layer on a pixel basis.
That is, white organic light emitting display devices are produced by depositing respective layers between an anode and a cathode without using a mask in the formation of light emitting diodes. The white organic light emitting display devices are characterized in that organic films including organic light emitting layers are sequentially formed by depositing different components for the films under vacuum conditions.
The organic light emitting display device may be utilized in a variety of applications including slim light sources, backlights of liquid crystal display devices or full-color display devices using color filters.
Meanwhile, conventional organic light emitting display devices include a plurality of stacks emitting different colors of light wherein each of the stacks includes a hole transport layer, a light emitting layer and an electron transport layer. In addition, each light emitting layer includes a single host and a dopant for rendering color of emitted light, to emit the corresponding color of light based on recombination of electrons and holes injected into the light emitting layer. In addition, a plurality of stacks, each including different colors of light emitting layers, are formed by lamination. In this case, a charge generation layer (CGL) is formed between the stacks so that electrons are received from the adjacent stack or holes are transported thereto. In addition, the charge generation layer is divided into an n-type charge generation layer and a p-type charge generation layer. A charge generation layer structure capable of improving both driving voltage and lifespan is desired.